Process of bleaching leather.



FIPSEUB .PATENT Ormea@ VILLIAM ll. KKRUG, OF YVASHINGTON, `DISTRICT `OF COLUMBIA JAMES HALEY, OF NEXV YORK, N. Y.

Paocess oF BLEACHING lglsiiTl-HER.v

,SPEEFICATQN forming part." of Letters Patent N o. 680,334, dated August v13;, y1190.15:V i" apprenait-ned May 8,1901. serai No. 59,310. (No specimens.) 't

T all '107mm may concern:

l?. e it known that We, 'WILLIAM Il. KRG, residingkat "Washington, in the District of Columbia, and EDWIN JAMES' HALEY, residing in the city, county, and State of New York, citizens of the United States, have invented y certain new and useful Improvementsin Processes of Bleaching Leather, of which the following 'is a specification.A l A bleaching liquor is first prepared by forming aigl'llleonssolution Qf tanning material in 'any Well-known manner, the strength of the solution depending upon the character of the leather and the tannery practice; but in our process the bleaching solution is preferably approximately of the same-or of greater 7Ndensity'than that to which the leather was last'subjected Yin the preceding tanning-"process.. 'To this soluti'onrpf tanning material nation of allaIr'ei-ngeedients not only sufficient toblarifythe same ordis'solve the insoluble constituents naturally present in the tanfving'material, butin such excess as to se- 'czre thebleaching effect desired-that is, the

' desired, and if the bleachingliquor'is formed of 'a solution obtained from a bark the pro 'y portion of alkaliwill be less than if it is `formed from someother materials, as quey bracho extract. The mixture thus obtained is then heated preferably to a temperature of between'lOOo and 140 Fahrenheit andis maintained during treatment at as nearly as pos- 'siblea uniform temperature and is als yeaintained as nearly as possible at a uniform' strength or density by adding at intervals such .quantities of tanning material and alkali -as are requisite for this purpose. The leather is immersed in the bleaching .liquor and 1smaintained therein for a short period of time, as from one to ten minutes or more, according to' theleharacter of thefl'eather and the el'l'eet desired, the immersion being` continued for a greater length of time tosecnre a denser product.

ln usingtlic terni alkali we nclndc there 1- which the tanningoperation has be:

by an alkali, alkaline salt, or alkaline ,com-A bination of ingredients-as, for instance,l`so

dium carbonate or borax or a combination thereof. I v y After the treatment in the alkaline bleaching-bath the leather is transferred toan acid-i bath. This acid-bath consists of a Weak aq'ueons solution of any suitable mineral or organic acid, as sulfuric or hydrochloric or ox'- 6o alicacid or a combination thereof, thc'solution varying in strength according` tothe char# acter of the leather and the densityof the bleaching alkalineliquorpreviously used, but

being maintained as nearly as possible at a uniform strength during the treatme'ntyof the mass of leather to secure uniform results? The acid-bath is preferably maintainediatas nearlyauniform temperature as possible-'say from 100 to 140O Fahrenheit-and the leather 7o is immersed therein and permitted to remain vfrom one to ten minutes or longer, according. 2'.

to the color and properties desired, thelonger immersion securing a lighter color and lre'a'vier i or denser leather. After the acid treatment the leather is'removed, drained, and'ivashed with Water to remove the acid. v-lt it'iisidek.; sired to modify theco'lor of the*lea'therafter this acid treatment, the leather niaybefimmersed in a soin-tion of tanningffmaterilal, 8o

either with or without the addition' f'a'lkali, andl beallowed to remain1therein,untilixthet desired color elfeet is attained. 'llhisrayfbe done before the leather is washed'witlrtyater.

In bleaching hemlock-tanned'.sole-leather 85 our process maybe carried out :1s-follows:

AAssuming that the tanning lifquerfin-tliejlast-` layer from which the leather-istakeutltt's a density o'" 40 barkometer, we make up an alkaline `nxac`ningbathfof a densit bai-kom eter `by dissolving ninety-twozpnunds of Quebracho extract, fonrteemfpounelw f a -=ra\', and twenty-eight ponnds'of,sodi-um" carbonate in every'ten cubic feetfofjvater,

(six hundred andtwenty-tive pounds. hath is heated` to '140O Fahrenlieit,and leather taken directly from the last jl pleted is immersed.' therein for iiyen ttes,

whereupon itis removed, drained fo .a few xo:

minutes, and then immersed in the acid-bath. which is prepared as follows: Five pounds' of ,AND antritt y This sulfuric scid are dissolved in every len. cnhic feet of water and the solution 'is heated to ,ll-il?" Fahrenheit. n this acid-bath the leather remains for-five minutes, whereupon it is re moved. and rinsed thoroughly in cold Water.

Vlihen operating on a large nu mber of sides, it is 'funn-1i necessary to strengthen seth 'the alkalinelileaehingdlatll and the acid-bai`n from time to time. lin/practice the density of the alkaline bath may'iall to all)C harlzoiueter, whereupon we add a sufficient quantity 'ot a very concentrated aqueous alkaline solution of Quebracho `extract containing the same ingredients as the alkaline 'bleachingn bath and in the same proportions until he -density ol the alkaline bleacl'ling-liath airain becomes 45 barkometer. The acidity of the acidbatii is" maintained by adding after eres-y li ,'y sides which have been immersed therein'from threeJsn'ths to tive-tenths ci a pound of sulfuric acid for every'len cnific feet-of water. li it is now desired to impart to 'this bleached leather an cali color, the leather is innnersed in apliquor made/from oal'carlc ,ln-wing a density of 40 harkometer and a temperature el 100o Fahrenheit and allowed lo remain therein until the desired color-is obtained.

The above sets forth speeilieally one appli cation of our in ventionj, but it is to be unf ders'tood that the invention is not limited thereto, as the particular ingredients, their particolar proportions in the baths, and the density and temperatures of the lil lhs de pend upon tannery practice.

i'lhe above-de: )ed treatmentresnlts in Very material ad intriges over the orrlliniry processes of bleaching. First, the leather instead of heilig reduced in weight is ini-iin tained or increased in weight, and conse-- quently is ol greater density, resulting in greater durability of the articles made there- Li'rcni; secondly, the bleach instead of being a surface bleach is one which may, isi prolonged, affect the entire fiber of the leather, so that 'lhearticles :nado therefrom will not vary in color from the effectsof Wear; thirdly, it is practicable hy Varying the strength of the solution to produce any desired shade, and therefore to operate upon a mass of leather with uniform results in this'respect.

As before stated, it is preferable to make use of an alkaline bleaching-bath in wnich the proportion of tanning material is1 stronger than that from which the leather was last taken in the preceding tanning operation; but it is possible te carry cnt onr process with a bleaching solution in which the tanning material is in a less proportion. The use of a bleaching solution consisting'of tanning nia-- terial, however, in connection with a snilicient quantity of alkali to produce the bleaching effect, instead of reducing the weight and secousse density ol.' the product, as'usual, will maintain or increase it, and in proportion as greater Weight is desired it is desirable to increase the proportion of tanning' material and alkali in the solution.

lVithout limiting ourselves to the precise temperature, proportions, and materials specified, we claimin the art of bleaching leather, the process substantially ss hereinbefore described, which consists in subjecting leather, after the tanning operations, to the action of a solution of tanning inaterial'and alkali, in which the -t-anninginaterial 'is approximately as strong as that 'to which the leather Was last subjected and in which the alkali is in excess of the amount necessary to clarify and suffin cient to produce the bleaching effect.

il, in, the art of bleaching leather, the process substantially' as hereinliefore described, which consists in subjecting leather, after the tanning operations, to the action of a solution ct tanning material and alkali, in which. the tanning;` material is approximately as strong as that, to which the leather was last subjected and in which the alkali is in excess ci the amount necessary to clarify and suiicientto prod nee the bleaching eliiect, and'then subjecting the leather tc the action of an acidiileth.

5. in the art of bleaching leather, the process substantially as hereinbeiore described, which consists in snhjecti ng leather, af ter the tanning operations, to the action of a solution ci tannini?, material and alkali, in which the tanning material is approximately as strong as that to which the leather Was last suole-etsii and in which the alkali is in excess ci' the amount necessary to clarify and suincient to produce the bleaching effect, thon subjecting the leather to the action ci an aciv 'yatluand then snlojecti ng the bl y' hed leather to a solution or. tan ning inaterial with or without 'the addition oit' alkali to change its crier.

1i. in the art of bleachingr leather, the process substantially hereinbefore described, which consists in subjecting the same, after tanning operations, to the action of a solution of tanning material and alkali, in which theproportion of tanning material is greater than in the last tanning liquor, and thereafter iinmersing in an acid-hath.

in testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses. i

WILIAM. H. KRU il. EDW'IN JAMES HALEY. iVitnesse-s as to William ll. Krug:

i?. LK FREEMAN, HENRY J. Guess. Witnesses as to Edwin'James Haley:

il. illALEY, .ANN W. Hanny, 

